Process of producing acrylonitrilenever dried cuprammonium cellulose rayon yarn graft polymers



United States Patent Office 3,373,125 Patented Mar. 12, 1968 This invention relates to a process of producing graft polymers and more particularly to a process of preparing graft polymers of acrylonitrile on a backbone of cuprammonium rayon fibers or yarns.

In United States Letters Patent No 2,922,768 to Mino and Kaizerman there is described a process of preparing graft polymers by polymerizing a polymerizable vinylidine monomer in an aqueous medium at a pH not greater than 3.5 and in the presence of a polymeric organic reducing agent, such as cellulose, and a ceric salt which is soluble in at least one component of the reaction medium. More specifically, there is described in the aforesaid patent a process in which the monomer is acrylonitrile and the polymeric organic reducing agent is dry cellulose.

Although it is possible to graft acrylonitrile monomer onto dry fibers and yarns, the physical properties of the grafted products viz., hydrophobic properties, bursting strength, abrasion resistance, hand, and dimensional stability, are commercially unsatisfactory due to the limited amount of monomer which can be grafted onto dry yarn.

It is therefore an object of this invention to provide a method of uniformly grafting large amounts of acrylonitrile monomer onto undried cuprammonium rayon fibers and yarns.

Other objects will readily be apparent to those skilled in the art from the following description of my invention.

Unexpectedly, I have found that considerably larger amounts of acrylonitrile monomer can be grafted uniformly onto cuprammonium rayon fibers and yarns when following the process of Mino and Kaizerman provided the grafting process is carried out on fresly spun, undried cuprammonium rayon yarns and fibers which are still in the gel state.

The acrylonitrile monomer is applied preferably from an aqueous bath containing a dissolved ceric catalyst. As disclosed by Mino and Kaizerman, the amount of the catalyst and the concentration of the monomer may vary; however, I prefer to use a solution containing about 5 percent of the monomer based on the volume of the bath and a ceric salt catalyst in the amount of about of the weight of the monomer. The ratio of bath volume to dry yarn preferably is from about 10:1 to about :1. The calculated volume of water retained by the yarn in the gel state is included in the volume of the bath.

The following examples illustrate the increased and uniform weight add-on of grafted monomer obtained by my invention.

Example I 150 denier cuprammonium rayon yarn, freshly spun and washed, was treated before having been dried in an aqueous bath containing ,5 percent acrylonitrile based on the volume of the bath (including the calculated volume of Water contained in the undried yarn) and .5 percent ceric ammonium nitrate catalyst based on the weight of the acrylonitrile. The dry yarn to bath volume ratio was 15 to 1. After treatment for 15 minutes, the yarn was washed and dried. Upon weighing, the increase of weight of the yarn based on the calculated dry weight of the untreated yarn was 82.5 percent.

Example 11 150 denier cuprammonium yarn which had been dried was treated for 15 minutes in a bath of the same composition and bath volume to dry yarn ratio as in Example I. After washing and drying the treated yarn, a weight increase of percent based on the calculated weight of the dry, untreated yarn was found.

Example III denier cuprammonium rayon yarn which has been Washed and dried twice, as is the case in the conventional processing of cuprammonium rayon yarn, was subjected to the same treatment as in Examples I and II. The weight increase of the yarn was 59 percent.

By varying the bath ratio, the amount of catalyst, and the monomer concentration, the amount of monomer grafted onto the yarn may be adjusted to the desired amount. Of course the denier of the yarn also affects the grafting process.

Although ceric ammonium nitrate is the preferred catalyst, other ceric salts disclosed in US. Patent No. 2,922,768 may be used.

Treated yarn was found to be immune to cuprammonium solution and dimethyl formamide which are solvents for cuprammonium rayon and polyacrylonitrile respectively. Thus, actual grafting rather than deposition of polymerized acrylonitrile on the yarn was affirmed.

The cuprammonium rayon of this invention may be produced by precipitation from a solution of cellulose in ammonical copper sulphate by the conventional spinning processes as disclosed, for example, in US. Patent No. 2,587,619 to Hofmann of Mar. 4, 1952. Of course in this process the yarn is treated before being dried.

The term gel state and yarn used in the claims accompanying this specification are intended to cover precipitated, purified filaments, yarns and fibers which have never been dried.

I claim:

1. The process of producing graft polymers which comprises reacting monomeric acrylonitrile dissolved in an aqueous medium at a pH not greater than 3.5 in the presence of a ceric salt with a freshly formed, never dried cuprammonium cellulose rayon yarn, said ceric salt being soluble in at least one component of said aqueous medium.

2. The process of producing graft polymers which comprises reacting monomeric acrylonitrile dissolved in an aqueous medium at a pH not greater than 3.5 in the presence of ceric ammonium nitrate with a freshly formed, never dried cuprammonium cellulose rayon yarn.

3. The process of producing graft polymers which comprises reacting monomeric acrylonitrile dissolved in an aqueous medium at a pH not greater than 3.5 in the cuprammonium cellulose rayon yarn, said ceric salt being soluble in at least one component of said aqueous medium, and said aqueous medium containing about five percent by volume of acrylonitrile monomer.

' 4. The process of producing graft polymers which oomprises reacting monomeric acrylonitrile dissolved in an aqueous medium at a pH not greater than 3.5 in the presence of a ceric salt With a freshly formed, never dried cuprammonium cellulose rayon yarn, said ceric salt being soluble in at least one component of said aqueous medium, said aqueous medium containing about five percent by volume of acrylonitrile monomer, and said ceric salt being present in the amount of about 0.5 percent based on the Weight of aerylonitrile monomer.

4 1 References Cited UNITED STATES PATENTS 2,902,391 9/1959 Daul et al. 8-1163 2,922,768 1/1960 Mino et al 26017.4 3,083,118 3/ 1963 Bridgeford.

FOREIGN PATENTS 886,552 1/ 1962 Great Britain.

WILLIAM H. SHORT, Primary Examiner.

V. A. MORGANSTERN, E. M. WOODBERRY,

Assistant Examiners. 

1. THE PROCESS OF PRODUCING GRAFT POLYMERS WHICH COMPRISES REACTING MONOMERIC ACRYLONITRILE DISSOLVED IN AN AQUEOUS MEDIUM AT A PH NOT GREATER THAN 3.5 IN THE PRESENCE OF A CERIC SALT WITH A FRESHLY FORMED, NEVER DRIED CUPRAMMONIUM CELLULOSE RAYON YARN, SAID CERIC SALT BEING SOLUBLE IN AT LEAST ONE COMPONENT OF SAID AQUEOUS MEDIUM. 